US3062640A

US3062640A - Method of operating a blast furnace

Info

Publication number: US3062640A
Application number: US61064A
Authority: US
Inventors: Jagdish C Agarwal; Charles M Sciulli; Robert L Stephenson
Original assignee: United States Steel Corp
Current assignee: United States Steel Corp
Priority date: 1960-10-07
Filing date: 1960-10-07
Publication date: 1962-11-06
Anticipated expiration: 1979-11-06
Also published as: GB978759A

Description

United States Jersey No Drawing. Filed Oct. 7, 1960, Ser. No. 61,064

2 Claims. (CI. 75-42) This invention relates to a method of operating a blast furnace and more particularly to the production of iron in which gaseous hydrocarbons are substituted for part of the coke ordinarily used. Many attempts have been made to reduce the amount of coke required in this manner. These methods were generally of two types; one in which the hydrocarbons were burned with air and/ or oxygen and the products of combustion then introduced into the blast furnace and the second in which the hydrocarbons were directly introduced into the tuyere zone of the blast furnace. To the best of our knowledge none of these attempts were successful. We believe that the failure of these attempts was-due to the failure to properly modify the coke charge and the temperature of the hot blast to compensate for the chilling effect of the hydrocarbons. In the presence of coke, hydrocarbons do not release suflicient' heat into the furnace to maintain the temperature normally present in the tuyere zone of the blast furnace. Thus, the priorpractices resulted in a loss of production.

It is therefore an object of our invention to provide a method of operating a blast furnace in which the coke charge and the temperature of the hot blast are so controlled as to produce pig iron efficiently.

This and other objects will be more apparent after referring to the following specification.

Assuming that the blast furnace is operating in a conventional method its operation will be modified in the following manner: From 2 to 6 hours before the injection of the hydrocarbons the coke charged per ton of hot metal is reduced and the hot blast temperature is raised. Specifically the usual coke charged per ton of hot metal is decreased by an amount equal to 0.8 to 1.0 mole of contained carbon in the coke for each mole of carbon in the injected hydrocarbons plus an amount equal to 0.2 to 0.4 mole of contained carbon for each mole of hydrogen in the injection hydrocarbons. The hot blast temperature is raised from 30 to 60 F. above the normal operating temperature (usually between 1000 F. and 1600 F. in conventional blast furnaces) for each mole of carbon removed from the coke per ton of hot metal on account of the injected hydrocarbons. The coke charged per ton of hot metal is then further reduced by an amount equal to 1.66 to 4.16 moles of contained carbon for each 100 F. increase in the hot blast temperature. The hydrocarbons are preferably injected through every tuyere of the furnace to eliminate localized chilling. If desired, /2 mole of high purity oxygen may be injected into the furnace per mole of carbon in the added hydrocarbons.

The coke rate and blast temperature achieved at the end of the transition period are maintained as long as the hydrocarbons are being introduced into the furnace.

In one particular procedure in which iron was produced in an experimental blast furnace having a 4 foot diameter hearth, a 20 foot stack and a 39 inch bosh, the furnace was operated with the burden consisting of sinter, coke, limestone, dolomite and gravel having the following analyses:

atent ice Sinter Coke Limestone Dolo- Gravel mite Fixed C 91. 1

It will be understood that the iron containing component may be ordinary ore, sintered ore or flue dust or any other conventional charge. The term iron ore will be used hereinafter to designate any of these iron bearing constituents. When operating the furnace without hydrocarbon injection the furnace was operated with a sinter to coke ratio of 2.3 and an oxidizing blast (including moisture) of 984 standard cubic ft. per minute at a temperature of 1730" F. The hot blast temperature was substantially higher than in a conventional blast furnace because of its small size with resultant high heat loss. A production rate of 1806 lbs. of hot metal per hour was obtained and 1336 lbs. of coke were consumed per ton of hot metal produced. When operating the furnace with a hydrocarbon injection (in the form of methane or natural gas) of approximately 38.3 cubic ft. per minute and a total blast of- 968.3 cubic ft. per minute at a hotblast temperature of 2014 F. a production rate of 1832 lbs. of hot metal per hour was obtained. The coke rate was reduced to 1117 lbs. of coke per ton of hot metal. The following table gives a comparison of the average operating data without hydrocarbon injection and with 4% methane injection.

TABLE II Comparison of Average Operating Data During Base Period and 4% Methane In ection Without With hydrohydrocarbon carbon 1. Dry Blast Air (5.0.1111) 978. 1 924. 4 2. Ambient Moisture in blast (s.c.f.m.)- 5. 9 5. 6 3, Methane Injected in blast (s.o.f.m.) 38. 3 4. Total Wet Blast (s.c.f.m.) 984 968.3 5. Average Hot Blast Temp. F.) 1, 730 2,014 6. Top Gas Analysis (dry):

CO 30. 2 27. 3 CO2 12. 1 12. 6 H2 0. 8 4. 4 N2 56. 3 55. 1 7. Top Gas Volume (sci. 1,375 1,312 8. Top Gas Temperature 592 644 9. Production Rate (lb. h.in./hr 1,806 1,832 10. Coke Rate (1b. eoke/t.h.m.) 1,336 1,117 11. Slag Volume (lb./t.h.m.) 573 669 12. Percent Si in metal 0. 86 0. 13. Percent S in rnetal 0.041 0.028 14. Hot Metal Temp. F 2, 420 2,413 15. Slag Temp. F.) 2,691 2,680

In arriving at the above operation it was first decided that the total blast should remain approximately constant and that the hydrocarbon addition should be approximately 4% of the wet air blast which was assumed to be 935 cu. ft. per minute. On this basis the hydrocarbon addition was calculated to be 2244 cu. ft. per hour. With a production rate of 1806 lb. per hour the hydrocarbon addition per ton of hot metal was calculated to be or 2480 cu. ft. at atmospheric pressure and 60 F. The number of moles of CH; is equal to correspondingly this resulted in 6.54 moles of carbon and 13.08 moles of hydrogen. On the basis of 0.8 mole of contained carbon per mole of carbon in the methane and 0.2 mole of contained carbon per mole of hydrogen in the methane the amount of carbon decrease per ton of hot metal was calculated to be 0.8 6.54+0.2 13.08 or 7.85 moles. n the basis of raising the desired blast temperature 40 F. per mole of carbon removed the desired blast temperature was calculated to be or 2044 F. It was decided to further reduce the amount of coke by an amount equivalent to 1.70 moles of contained carbon per 100 F. increase in blast temperature. This amounted to 5.34 moles. On this bases the total reduction in coke per ton of hot metal amounted to (7.85+5.34) 12+.91 or 174 lbs. With the foregoing as the basis for the changes in operating conditions the coke rate was lowered and the blast temperature was raised. Minor changes were made in the burden and blast temperature as are common in the operation of blast furnaces to obtain best operating conditions. As a result it was determined that the furnace worked best under the conditions set forth in Table II.

When oxygen is injected it is preferred to add the oxygen directly to the oxidizing blast. The use of oxygen increases the production rate.

While one embodiment of our invention has been shown and described, it will be apparent that other adaptations and modifications may be made Without depart ing from the scope of the following claims.

We claim:

1. The method of operating a blast furnace which comprises charging coke, limestone and iron ore into the top of the furnace, introducing hydrocarbons and an oxidiz- 5 ing blast into the furnace at the tuyeres, reducing the amount of coke charged from that normally used without hydrocarbon addition, the amount of coke reduction per ton of hot metal produced being equal to between 0.8 and 1.0 mole of contained carbon per mole of carbon in said hydrocarbons plus 0.2 to 0.4 mole of contained carbon per mole of hydrogen in said hydrocarbons, raising the blast temperature above normal between 30 F. and 60 F. per each mole of carbon in the said coke decreased per ton of hot metal, and further reducing the amount of coke per ton of hot metal an amount equal to 1.66 to 4.16 moles of contained carbon per 100 F. increase in the oxidizing blast temperature.

2. The method of operating a blast furnace according to claim 1 in which the oxidizing blast includes air enriched with oxygen, the amount of oxygen being at least approximately /2 mole per mole of carbon in said hydrocarbons.

References Cited in the file of this patent UNITED STATES PATENTS Kendall May 25, 1886 Kinney May 13, 1947 Pomykala Sept. 27, 1955 Raick Dec. 20, 1955

Claims

1. THE METHOD OF OPERATING A BLAST FURNACE WHICH COMPRISES CHARGING COKE, LIMESTONE AND IRON ORE INTO THE TOP OF THE FURNACE, INTRODUCING HYDROCARBONS AND AN OXIDIZING BLAST INTO THE FURNACE AT THE TUYERES, REDUCING THE AMOUNT OF COKE CHARGED FROM THAT NORMALLY USED WITHOUT HYDROCARBON ADDITION, THE AMOUNT OF COKE REDUCTION PER TON OF HOT METAL PRODUCED BEING EQUAL TO BETWEEN 0.8 AND 1.0 MOLE OF CONTAINED CARBON PER MOLE OF CARBON IN SAID HYDROCARBONS PLUS 0.2 TO 0.4 MOLE OF CONTAINED CARBON PER MOLE OF HYDROGEN IN SAID HYDROCABONS, RAISING THE BLAST TEMPERATURE ABOVE NORMAL BETWEEN 30*F. AND 60*F. PER EACH MOLE OF CARBON IN THE SAID COKE DECREASED PER TON OF HOT METAL, AND FURTHER REDUCING THE AMOUNT OF COKE PER TON OF HOT METAL AN AMOUNT EQUAL TO 1.66 TO 4.16 MOLES OF CONTAINED CARBON PER 100*F. INCREASE IN THE OXIDIZING BLAST TEMPERATURE.